A Novel Long-Range Passive UHF RFID System over Twisted-pair Cable

Radio Frequency Identification (RFID) is one of the most representative, rapidly growing, and highly extendable technologies, which uses electromagnetic waves in accordance with specific communications standards and regulations to identify, track, or even localise desired objects. However, due to its high cost, limited read range, and uncertain reliability, its adoption still lags, especially in large-scale organisations. Even though an RFID distributed antenna system (DAS) can greatly improve the detection range and read rate of a single reader when system uses different combinations of antenna states with frequency and phase hopping, the lossy and heavy coaxial cables between reader and antennas still limits the system coverage and design flexibility for wide-area passive UHF RFID applications. In order to develop a cost-efficient and flexibly-installed passive RFID DAS, a novel large-range passive UHF RFID system over twisted-pair cable is proposed in this dissertation. This new system consists of one baseband central controller and one antenna subsystem, connected by a commonly used twisted-pair cable. It is shown that transmitting/receiving low frequency baseband signals over a twisted-pair cable can significantly reduce cable attenuation and extend the communication distance. A simulation is conducted to demonstrate that frequency and phase hopping can also be remotely controlled to fit this system structure by slightly varying the frequency or phase of the input reference signal of the frequency synthesis system. The features of twisted-pair cable in terms of its low cost, light weight, and bend radius greatly improve the design and installation flexibility of an RFID system. The implemented system is designed based on the ISO 18000-6C and EPC Class 1 Generation 2 standards, and can operate according to FCC (902-928 MHz) and ETSI (865-868MHz) regulations. The results of the measurement show the reader can achieve a sensitivity of - 94.5 dBm over 30 m Cat5e cable, and its sensitivity can still remain at around -94.2 dBm over 150 m Cat5e cable. The experimental results of tag detection show that the passive tags can be successfully detected over a 6 m wireless range following a 300 m of twisted-pair cable between the central controller and antenna. This detection range cannot be achieved by existing commercial RFID systems. Since the transmission and reception in a RFID system are simultaneous, finite isolation of the circulator/directional coupler and environmentally dependent reflection ratio of the antenna lead to serious leakage problems. Leakage can directly cause sensitivity degradation due to saturation of the RF components. A fast leakage suppression block is developed in efforts to solve this problem. Measurements show that this new canceller can deliver an average suppression of 36.9 dB, and this excellent performance remains when the system uses frequency hopping. With help of an improved scanning algorithm, this canceller can find its optimal status within 38 ms, and this settling time is short enough for most commercial RFID readers. By reducing the number of voltage samples taken, the convergence time can be further improved. To fully investigate this new passive UHF RFID system value, a comparison study between the new system and a commercial system is conducted. This new automatic passive UHF RFID system is confirmed to deliver high performance long-range passive tag detection. Particular advantages are shown in the fast tag read rate and capability of uplink SNR improvement. This novel system is also superior to conventional RFID systems in terms of link distance, link cost, and installation flexibility

Front End of a 900MHz RFID for Biological Sensing

This thesis presents the front end of a 900MHz passive RFID for biological sensing. The components blocks of the front end consist of power harvester, switch capacitor voltage regulator, phase lock loop and a modulator and demodulator. As the RFID is passive so the power resource is limited hence the main focus while implementing all the block was low power and high efficiency power conversion. All the individual block were optimized to provide maximum efficiency. For the harvester to achieve high efficiency and high output voltage a design approach is discussed by which the device sizes are optimized and the values of the matching network components are solved. The efficiency achieved with this approach is 34% while supplying 74�[email protected]. The switch capacitor voltage regulator would supply power to the digital core of the RFID, which will operate at subtheshold or moderate inversion. The switch capacitor implemented in this work is a adaptive voltage regulator, as I intend to use the dynamic supply voltage scaling technique to compensate for the reduction in reliability of performance of the circuit due to variation of VTH across process due to random doping effects and temperature in subthreshold.The phase lock loop (PLL) block in this front end provide the system clock synchronized with the base station to all the backend blocks like the digital controller, memory, and the analog to digital converter ADC and the switch capacitor voltage regulator. The PLL is a low power with jitter of 24nsec and is capable of clock data recovery from EPC gen 2 protocol format data and consumes 3�W of power Finally a ultra low power AM (amplitude modulation) demodulator is presented which is consumes only 100nW and is capable of demodulating a double-sideband amplitude modulated (DSB-AM) signal centered at 900MHz and the modulating frequency is 160KHz. The demodulator can demodulate signal having as low as -5dBm power and 50% modulation index. The modulation for transmitting signal is achieved by BPSK(back scatter phase shift keying).Electrical Engineerin

Ultra Low Power IEEE 802.15.4/ZIGBEE Compliant Transceiver

Low power wireless communications is the most demanding request among all wireless users. A battery life that can survive for years without being replaced, makes it realistic to implement many applications where the battery is unreachable (e.g. concrete walls) or expensive to change (e.g underground applications). IEEE 802.15.4/ZIGBEE standard is published to cover low power low cost applications, where the battery life can last for years, because of the 1% duty cycle of operation. A fully integrated 2.4GHz IEEE802.15.4 Compliant transceiver suitable for low power, low cost ZIGBEE applications is implemented. Direct conversion architecture is used in both Receiver and Transmitter, to achieve the minimum possible power and area. The chip is fabricated in a standard 0.18um CMOS technology. In the transmit mode, the transmitter chain (Modulator to PA) consumes 25mW, while in the receive mode, the iv receiver chain (LNA to Demodulator) consumes 5mW. The Integer-N Frequency Synthesizer consumes 8.5mW. Other Low power circuits are reported; A 13.56 Passive RFID tag and a low power ADC suitable for Built-In-Testing applications

Sistemas eficientes de transmissão de energia sem-fios e identificação por radiofrequência

Doutoramento em Engenharia EletrotécnicaIn the IoT context, where billions of connected objects are expected to be ubiquitously deployed worldwide, the frequent battery maintenance of ubiquitous wireless nodes is undesirable or even impossible. In these scenarios, passive-backscatter radios will certainly play a crucial role due to their low cost, low complexity and battery-free operation. However, as passive-backscatter devices are chiefly limited by the WPT link, its efficiency optimization has been a major research concern over the years, gaining even more emphasis in the IoT context. Wireless power transfer has traditionally been carried out using CW signals, and the efficiency improvement has commonly been achieved through circuit design optimization. This thesis explores a fundamentally different approach, in which the optimization is focused on the powering waveforms, rather than the circuits. It is demonstrated through theoretical analysis, simulations and measurements that, given their greater ability to overcome the built-in voltage of rectifying devices, high PAPR multi-sine (MS) signals are capable of more efficiently exciting energy harvesting circuits when compared to CWs. By using optimal MS signals to excite rectifying devices, remarkable RF-DC conversion efficiency gains of up to 15 dB with respect to CW signals were obtained. In order to show the effectiveness of this approach to improve the communication range of passive-backscatter systems, a MS front-end was integrated in a commercial RFID reader and a significant range extension of 25% was observed. Furthermore, a software-defined radio RFID reader, compliant with ISO18000-6C standard and with MS capability, was constructed from scratch. By interrogating passive RFID transponders with MS waveforms, a transponder sensitivity improvement higher than 3 dB was obtained for optimal MS signals. Since the amplification and transmission of high PAPR signals is critical, this work also proposes efficient MS transmitting architectures based on space power combining techniques. This thesis also addresses other not less important issues, namely self-jamming in passive RFID readers, which is the second limiting factor of passive-backscatter systems. A suitable self-jamming suppression scheme was first used for CW signals and then extended to MS signals, yielding a CW isolation up to 50 dB and a MS isolation up 60 dB. Finally, a battery-less remote control system was developed and integrated in a commercial TV device with the purpose of demonstrating a practical application of wireless power transfer and passive-backscatter concepts. This allowed battery-free control of four basic functionalities of the TV (CH+,CH-,VOL+,VOL-).No contexto da internet das coisas (IoT), onde são esperados bilhões de objetos conectados espalhados pelo planeta de forma ubíqua, torna-se impraticável uma frequente manutenção e troca de baterias dos dispositivos sem fios ubíquos. Nestes cenários, os sistemas radio backscatter passivos terão um papel preponderante dado o seu baixo custo, baixa complexidade e não necessidade de baterias nos nós móveis. Uma vez que a transmissão de energia sem fios é o principal aspeto limitativo nestes sistemas, a sua otimização tem sido um tema central de investigação, ganhando ainda mais ênfase no contexto IoT. Tradicionalmente, a transferência de energia sem-fios é feita através de sinais CW e a maximização da eficiência é conseguida através da otimização dos circuitos recetores. Neste trabalho explora-se uma abordagem fundamentalmente diferente, em que a otimização foca-se nas formas de onda em vez dos circuitos. Demonstra-se, teoricamente e através de simulações e medidas que, devido à sua maior capacidade em superar a barreira de potencial intrínseca dos dispositivos retificadores, os sinais multi-seno (MS) de elevado PAPR são capazes de excitar os circuitos de colheita de energia de forma mais eficiente quando comparados com o sinal CW tradicional. Usando sinais MS ótimos em circuitos retificadores, foram verificadas experimentalmente melhorias de eficiência de conversão RF-DC notáveis de até 15 dB relativamente ao sinal CW. A fim de mostrar a eficácia desta abordagem na melhoria da distância de comunicação de sistemas backscatter passivos, integrou-se um front-end MS num leitor RFID comercial e observou-se um aumento significativo de 25% na distância de leitura. Além disso, desenvolveu-se de raiz um leitor RFID baseado em software rádio, compatível com o protocolo ISO18000-6C e capaz de gerar sinais MS, com os quais interrogou-se transponders passivos, obtendo-se ganhos de sensibilidade dos transponders maiores que 3 dB. Uma vez que a amplificação de sinais de elevado PAPR é uma operação crítica, propôs-se também novas arquiteturas eficientes de transmissão baseadas na combinação de sinais em espaço livre. Esta tese aborda também outros aspetos não menos importantes, como o self-jamming em leitores RFID passivos, tido como o segundo fator limitativo neste tipo de sistemas. Estudou-se técnicas de cancelamento de self-jamming CW e estendeu-se o conceito a sinais MS, tendo-se obtido isolamentos entre o transmissor e o recetor de até 50 dB no primeiro caso e de até 60 dB no segundo. Finalmente, com o objetivo de demonstrar uma aplicação prática dos conceitos de transmissão de energia sem fios e comunicação backscatter, desenvolveu-se um sistema de controlo remoto sem pilhas, cujo protótipo foi integrado num televisor comercial a fim de controlar quatro funcionalidades básicas (CH+,CH-,VOL+,VOL-)

Sensor-based management systems based on RFID technology

Παρατηρήσεις έκδοσης: λείπουν οι σελίδες 78, 102 από το φυσικό τεκμήριο.In this diploma thesis, the RFID technology is analyzed (operating principles, readers' and tags hardware, coding, modulation, anticollision procedures, frequencies, standards, applications). Moreover, a protocol to synchronize readers working in a multi-reader multi-tag environment is proposed. The protocol is applied to the store shelf scanning application and further refined to meet the requirements of this specific application

RFID multiantenna systems for wireless communications and sensing

Many scientific, industrial and medical applications require the measurement of different physical parameters in order to collect information about the spatially distributed status of some process. Very often this information needs to be collected remotely, either due to the spatial dispersion of the measurement points or due to their inaccessibility. A wireless embedded self-powered sensor may be a convenient solution to be placed at these inaccessible locations. This thesis is devoted to study the analytical relation governing the electromagnetic coupling between a reader and a embeddable self-powered sensor, based on radio frequency identification (RFID) technology, which is capable of wirelessly retrieving the status of physical parameters at a remote and inaccessible location. The physical parameter to be sensed may be the electromagnetic (EM) field existing at that location (primary measurement) or the indirect measurement of other parameters such as the temperature, humidity, etc. (secondary measurement). Given the simplicity of the RFID solution (highly embeddable properties, scavenging capabilities, penetration and radio coverage characteristics, etc.) the measurement can be done at a single location, or it can be extended to a set of measuring locations (an array or grid of sensors). The analytical relation is based on a reciprocity formulation studying the modulation of the scattered field by the embedded sensor in relation with the incident field, and allows to define a set of quality parameters of interest for the optimum design of the sensors. Particular attention is given to the scavenging circuitry as well as to the antenna design relevant to the sensing objective. In RFID tags, the existence of an RF harvesting section is an improvement with respect to conventional scattering field probes since it removes the need of DC biasing lines or optical fibers to modulate the sensor. However, this harvesting section introduces non-linearities in the response of the sensor, which requires a proper correction to use them as EM-field probes, although the characterization of the non-linearities of the RFID tag cannot be directly done using a conventional vector network analyzer (VNA), due to the requirements of an RFID protocol excitation. Due to this, this thesis proposes an alternative measurement approach that allows to characterize the different scattering states used for the modulation, in particular its non-linear behavior. In addittion, and taking this characterization as the starting point, this thesis proposes a new measurement setup for EM-field measurements based on the use of multiple tones to enlarge the available dynamic range, which is experimentally demonstrated in the measurement of a radiation pattern, as well as in imaging applications. The RFID-based sensor response is electromagnetically sensitive to the dielectric properties of its close environment. However, the governing formulation for the response of the probe mixes together a set of different contributions, the path-loss, the antenna impedance, the loads impedance, etc. As a consequence, it is not possible to isolate each contribution from the others using the information available with a conventional RFID sensor. This thesis mathematically proposes and experimentally develops a modification of the modulation scheme to introduce a new set of multi-load scattering states that increases the information available in the response and properly isolate each term. Moreover, this thesis goes a step forward and introduces a new scattering state of the probe sensitive to temperature variations that do not depend on the environment characteristics. This new configuration enables robust environmental sensing in addition to EM-field measurements, and sensing variations of the dielectric properties of the environment

Learning-Based Hardware Design for Data Acquisition Systems

This multidisciplinary research work aims to investigate the optimized information extraction from signals or data volumes and to develop tailored hardware implementations that trade-off the complexity of data acquisition with that of data processing, conceptually allowing radically new device designs. The mathematical results in classical Compressive Sampling (CS) support the paradigm of Analog-to-Information Conversion (AIC) as a replacement for conventional ADC technologies. The AICs simultaneously perform data acquisition and compression, seeking to directly sample signals for achieving specific tasks as opposed to acquiring a full signal only at the Nyquist rate to throw most of it away via compression. Our contention is that in order for CS to live up its name, both theory and practice must leverage concepts from learning. This work demonstrates our contention in hardware prototypes, with key trade-offs, for two different fields of application as edge and big-data computing. In the framework of edge-data computing, such as wearable and implantable ecosystems, the power budget is defined by the battery capacity, which generally limits the device performance and usability. This is more evident in very challenging field, such as medical monitoring, where high performance requirements are necessary for the device to process the information with high accuracy. Furthermore, in applications like implantable medical monitoring, the system performances have to merge the small area as well as the low-power requirements, in order to facilitate the implant bio-compatibility, avoiding the rejection from the human body. Based on our new mathematical foundations, we built different prototypes to get a neural signal acquisition chip that not only rigorously trades off its area, energy consumption, and the quality of its signal output, but also significantly outperforms the state-of-the-art in all aspects. In the framework of big-data and high-performance computation, such as in high-end servers application, the RF circuits meant to transmit data from chip-to-chip or chip-to-memory are defined by low power requirements, since the heat generated by the integrated circuits is partially distributed by the chip package. Hence, the overall system power budget is defined by its affordable cooling capacity. For this reason, application specific architectures and innovative techniques are used for low-power implementation. In this work, we have developed a single-ended multi-lane receiver for high speed I/O link in servers application. The receiver operates at 7 Gbps by learning inter-symbol interference and electromagnetic coupling noise in chip-to-chip communication systems. A learning-based approach allows a versatile receiver circuit which not only copes with large channel attenuation but also implements novel crosstalk reduction techniques, to allow single-ended multiple lines transmission, without sacrificing its overall bandwidth for a given area within the interconnect's data-path

Intelligent Sensor Networks

In the last decade, wireless or wired sensor networks have attracted much attention. However, most designs target general sensor network issues including protocol stack (routing, MAC, etc.) and security issues. This book focuses on the close integration of sensing, networking, and smart signal processing via machine learning. Based on their world-class research, the authors present the fundamentals of intelligent sensor networks. They cover sensing and sampling, distributed signal processing, and intelligent signal learning. In addition, they present cutting-edge research results from leading experts

RF techniques for IEEE 802.15.4: circuit design and device modelling

The RF circuitry in the physical layer of any wireless communication node is arguably its most important part. The front-end radio is the hardware that enables communication by transmitting and receiving information. Without a robust and high performance front-end, all other higher layers of signal processing and data handling in a wireless network are irrelevant. This thesis investigates the radio circuitry of wireless-networked nodes, and introduces several proposals for improvement. As an emerging market, analysis starts by examining available and ratified network standards suitable for low power applications. After identifying the IEEE 802.15.4 standard (commercially known as ZigBee) as the one of choice, and analysing several front-end architectures on which its transceiver circuitry can be based, an application, the Tyre Pressure Monitoring System (TPMS) is selected to examine the capabilities of the standard and its most suitable architecture in satisfying the application’s requirements. From this compatibility analysis, the most significant shortcomings are identified as interference and power consumption. The work presented in this thesis focuses on the power consumption issues. A comparison of available high frequency transistor technologies concludes Silicon CMOS to be the most appropriate solution for the implementation of low cost and low power ZigBee transceivers. Since the output power requirement of ZigBee is relatively modest, it is possible to consider the design of a single amplifier block which can act as both a Low Noise Amplifier (LNA) in the receiver chain and a Power Amplifier (PA) on the transmitter side. This work shows that by employing a suitable design methodology, a single dual-function amplifier can be realised which meets the required performance specification. In this way, power consumption and chip area can both be reduced, leading to cost savings so vital to the widespread utilisation of the ZigBee standard. Given the importance of device nonlinearity in such a design, a new transistor model based on independent representation of each of the transistor’s nonlinear elements is developed with the aim of quantifying the individual contribution of each of the transistors nonlinear elements, to the total distortion. The methodology to the design of the dual functionality (LNA/PA) amplifier starts by considering various low noise amplifier architectures and comparing them in terms of the trade-off between noise (required for LNA operation) and linearity (important for PA operation), and then examining the behaviour of the selected architecture (the common-source common-gate cascode) at higher than usual input powers. Due to the need to meet the far apart performance requirements of both the LNA and PA, a unique amplifier design methodology is developed The design methodology is based on simultaneous graphical visualisation of the relationship between all relevant performance parameters and corresponding design parameters. A design example is then presented to demonstrate the effectiveness of the methodology and the quality of trade-offs it allows the designer to make. The simulated performance of the final amplifier satisfies both the requirements of ZigBee’s low noise and power amplification. At 2.4GHz, the amplifier is predicted to have 1.6dB Noise Figure (NF), 6dBm Input-referred 3rd-order Intercept Point (IIP3), and 1dB compression point of -3.5dBm. In low power operation, it is predicted to have 10dB gain, consuming only 8mW. At the higher input power of 0dBm, it is predicted to achieve 24% Power-Added Efficiency (PAE) with 8dB gain and 22mW power consumption. Finally, this thesis presents a set of future research proposals based on problems identified throughout its development